The three male elephants and 15 females live in the Big Game Parks
in the southern African nation.
Last month, the U.S. Fish and Wildlife Service approved
their relocation to three facilities: the Dallas Zoo, the Sedgwick County Zoo in Wichita, Kansas, and the Henry Doorly Zoo in Omaha, Nebraska.
The animals were set to be culled as part of a plan to make room for rhinos at the Swaziland facilities, the zoos said in a statement.
In exchange for the elephants, the U.S. zoos will donate funds toward the rhino conservation efforts at the Big Game Parks.
"The zoos are working quickly to bring the elephants out of Swaziland, where historic drought conditions continue to threaten wildlife," the statement said.
The plan has sparked an outcry from conservationists and rights groups, who say relocating the giant animals to zoos half a world away is detrimental to their health.
Dozens of conservationists from all over the world
signed a letter posted on the website of the Conservation Action Trust, saying the animals are better off in their natural habitat.
They accused the zoos of using Swaziland to add on to their elephant populations.
"Elephants are highly intelligent, sensitive, and social. That they suffer in captivity is beyond serious debate," the letter said. "For the 18 elephants targeted for importation, it is no exaggeration to conclude that they face a sad, uncertain future."
Other animal rights groups, including PETA,
have also criticized the planned transfer, saying the zoos are not equipped to handle the animals.
Zoos defend move
Despite the controversy, the zoos plan to
provide homes for the elephants.
"Our zoos are committed to the safe future of these elephants," said Gregg Hudson, president of the Dallas Zoo.
He said the zoos will ensure that elephants in the same social circles remain together. Their facilities are spacious enough for the giant animals to roam and forage, the zoos said.
"We are making a lifetime commitment to these elephants and their offspring and are providing a safe home for them," said Dennis Pate, president of Omaha's Henry Doorly Zoo.
The wildlife service said elephants have been relocated by air from Swaziland to the United States before. It's unclear when the 18 elephants will make the trip.